The subject of this invention is a fluid seal particularly for use in situations where the seal is to be broken and remade repeatedly, for example for providing a seal around the obturator member of a butterfly or other type valve when the obturator has been rotated into the closed position, transverse to the axis of the fluid passage through the valve.
The normal type of seal particularly as used in butterfly and gate valves consists of a plain strip of resilient material such as natural or artificial rubber. Such a sealing strip by its own resilience can deform sufficiently within its own bulk, i.e., by changing its cross-sectional shape to provide an excellent seal. A seal of material as soft as rubber is, however, unsuitable in certain situations simply by reason of the softness and high resiliency of the material. For example, where the seal is to resist high pressures the material of the seal must be comparatively hard to avoid extrusion of the seal. In such situations it is customary to use certain synthetic materials, one suitable material being a fluorocarbon resin such as polytetrafluoroethylene. This material is, however, incapable of deforming sufficiently under the valve closure force normally available to provide the required sealing characteristics so that special and expensive precision machining of the obturator and the sealing strip are necessary to obtain a good seal.
It is an object of the present invention to provide a fluid seal which is capable of providing a good seal even when formed of comparatively rigid material.